How to choose a machine tap?

A tap is an essential tool for machining and is used to create internal threads in straight holes. When cutting a thread, we must first clarify whether we want to cut the thread manually or by machine and what type of thread we will need. A machine tap saves us time because it is faster and, compared to hand taps, does not have to be replaced during work. A machine tap, as the name suggests, cuts with the help of a machine. It can be clamped using a chuck or thread cutting head in a bench or column drill, CNC machine, but of course also in a hand drill.
When choosing the right tap, it is essential to know whether we will create a thread in a through or non-through (blind) hole. A through hole passes through the entire workpiece, while a blind hole, on the other hand, ends at a certain depth in the workpiece and is not through.

TAP DIVISION

STRAIGHT FLUTE TAP
A straight flute tap is designed for through holes, but it can also be used for blind holes that are not as deep. A tap with a straight flute and a spiral point is even more widely used and is designed only for through holes. The spiral point breaks and shoots the chips out of the hole. The groove will also serve us here for a better flow of coolant.

SPIRAL FLUTE TAP
A spiral flute tap, or twisted tap, is used for tapping into blind holes. The spiral guides the resulting chips out of the hole and upwards. This eliminates damage to the cut thread and the tap itself.

If we are not sure whether the hole will be through or blind, it is better to choose a straight flute tap.

FORMING TAP
It does not cut the thread, but forms it. Forming with a forming tap only works with sufficiently ductile materials, but it has a longer service life and creates a deeper and stronger hole. It is a cold machine threading. It is not entirely suitable for some types of materials. It has an advantage especially in non-through holes, as there is no risk of the hole being clogged with chips. Forming does not disrupt the fibers in the material profile as with conventional cutting.

THREAD TYPES
M – metric thread
MF – metric fine thread
G – pipe thread
UNC – unified coarse thread
UNF – unified fine thread

BY MATERIAL
It is important to know what kind of material you will be machining. As a standard, taps are made of high-speed steel (HSS) or high-speed steel with 5% cobalt, known as HSSco5 (HSSE).

It depends on the material being machined. The offer includes taps for:
steels with a strength of up to 500 N/mm2
steels with a strength of up to 800 N/mm2
stainless steels
refined and alloyed steels with a strength of up to 1100 N/mm2
refined and alloyed steels with a strength of up to 1400 N/mm2
gray cast iron
aluminum
universal use

Surface treatments and coatings
For even better results, we can use coated taps. They are available with TiN (Titanium Nitride - golden yellow), TiCN (Titanium Carbonitride - blue-gray), TiAlN (Titanium Aluminum Nitride - purple-gray) or OX (Oxidized - dark gray) coatings.

You can read more information in our NASTROJE CZ catalogue, page 301.

IMPORTANT POINTS FOR CUTTING THREADS:
1) Pre-drill the hole with a drill (it must always be smaller than the desired thread, you can use our sets - tap + drill)
2) Countersink the hole with a countersink (it will make it easier to insert the tap and ensure a better start to cutting the thread)
2) Place the machine tap in the machine
3) Use cutting oil or paste (it will extend the life of the tap and improve the quality of the cut surface)
4) Slowly insert the tap into the drilled hole, maintain and control the correct pressure
5) Carefully remove the tap

We recommend wearing protective gloves and glasses during this work. Protective equipment will protect us from chips and sharp edges.

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